Typical end closures for beer and beverage containers have an opening panel and an attached leverage tab for pushing the opening panel into the container to open the end. The container is typically a drawn and ironed metal can, usually constructed from a thin plate of aluminum or steel. End closures for such containers are also typically constructed from a cutedge of thin plate of aluminum, formed into a blank end, and manufactured into a finished end by a process often referred to as end conversion. These ends are formed in the process of first forming a cutedge of thin metal, forming a blank end from the cutedge, and converting the blank into an end closure which may be seamed onto a container.
These types of container ends have been used for many years, with almost all such ends in use today being the “ecology” or “stay-on-tab” (“SOT”) ends in which the tab remains attached to the end after a tear panel, including large-opening ends (“LOE”), is opened. The tear panel being a portion of the can end defined by a primary score line or length. The tear panel may be opened, that is the score may be severed, and the tear panel displaced at an angular orientation relative to the remaining portion of the can end. The tear panel remains hingedly connected to the remaining portion of the can end by a hinge segment, leaving an opening through which the user draws the contents of the container. In an LOE, the opening is typically at least 0.5 square inches in area, but in more recently developed ends, LOE-type openings have had areas less than 0.5 square inches.
It is also well known to provide a secondary score line of lesser depth than the primary score line. This score line, commonly referred to as an “antifracture score” is provided to reduce residual stresses associated with the primary score line so as to prevent or minimize the occurrence of microcracks in, or premature fracture along, the primary score line.
Opening of the tear panel is operated by the tab which is attached to the can end by a rivet. The tab is attached to the can end such that a nose of the tab extends over a proximal portion of the tear panel. A lift end of the tab is located opposite the tab nose and provides access for a user to lift the lift end, such as with the user's finger, to force the nose against the proximal portion of the tear panel.
When the tab nose is forced against the tear panel, the score initially ruptures at a vent region of the score. This initial rupture of the score is primarily caused by the lifting force on the tab resulting in lifting of a central region of the can end, immediately adjacent the rivet. As the tab is lifted further, the score rupture propagates along the length of the score, eventually stopping at the hinge segment.
To improve openability of the can end, manufacturers first designed tear panels with circumferential emboss beads to stiffen the tear panel. However, tear panels having an emboss bead have a tendency to dome or bulge when the beverage container is pressurized. Thus, the tear panel must be pushed back through the pour open upon opening. This required an increased amount of pressure to snap the tear panel through the pour opening. When beverage can manufacturers began producing can ends with larger pour openings, and consequently larger tear panels, this increase in required opening force became an issue or problem. These LOEs have a greater tendency to bulge due to their much greater surface area.
The circumferential emboss bead generally gave way to a down panel on the center portion of the tear panel to further improve openability. The down panel was developed to lower the magnitude of the force required to open the tear panel, especially on LOEs. The down panel generally does not bulge. This keeps the score flat. When the score is flat, the pour panel does not have to pass back though the pour opening as the can end is opened. The down panel produced a concave effect upon initial opening. This allowed score on LOE's to shear easier or with less force.
However, prior to pressurization, LOEs have a tendency to exhibit an upward dome. This causes a nose portion of the tab to ride a little high. When the LOEs are stacked, this high riding tab nose causes sponginess in the can end stacking. This sponginess can lead to miscounts of ends in a sleeve of stacked ends or can lead to longer sleeves than if the sponginess did not occur. For example, 4 to 5 inch differences in bag or sleeve length from one sleeve to the next can be experienced based on the sponginess of the stack.
Additionally, the contact between the tab and the product side of the adjacent, or next stacked, can end may encourage manufacturers to produce tabs with less height and less perfectly formed curved edges. Such tabs may have less height, but also has less strength for opening the can end.
The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior can ends of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings.